1. Field of the Invention
This invention relates to magnetic tape drives; and more particularly, to a tape cartridge drive with an improved cartridge door opening mechanism.
2. Description of the Prior Art
In recent years, computer technology has greatly expanded the market for computers, including reasonably inexpensive small computers, such a personal computers and computers for small businesses. The so-called floppy disk drives provide a common means of data storage for small computers. One floppy disk drive in common use today is the industry standard 51/4 inch minifloppy disk drive. One or more of these disk drives are typically mounted inside the computer console. A diskette is inserted or removed through one or more slots in the front of the console. In other applications, the minifloppy disk drive is contained in a separate housing for use externally to the computer console. In either instance, it has become an industry practice to provide a 51/4 inch minifloppy disk drive as a package with standard exterior dimensions.
Floppy disk drives have proved to be convenient for many applications, such as program loading and data interchange, but they have a limited data storage capacity. Because of this problem, larger capacity disk drives, such as the so-called Winchester disk drives, have been used in lieu of floppy disk drives in applications requiring greater data storage capacities. The Winchester-type disk drive generally comprises one, two, or three hard disks on which data are recorded. A Winchester-type disk drive can provide a much higher data storage capacity and faster data access and data transfer times than a floppy disk drive. Accordingly, a common practice in small business applications is to use a combination of the minifloppy disk and the Winchester disk. In this way, the day's transactions can be recorded on one or two floppy disks, and a full copy of the business's transactions can be made on a hard disk at weekly intervals or longer.
Recently, Winchester-type disk drives have been manufactured in a package with the same exterior dimensions and mounting hole locations as a standard 51/4 inch minifloppy disk drive. In this way, the Winchester disk drive can be conveniently installed in the computer console in place of a minifloppy disk drive to provide the larger data storage capacity.
Data storage for computer applications also can be provided by magnetic tape drives instead of disk drives. In recent years, 1/4-inch cartridge tape drives have been replacing floppy disk drives in many applications because the tape cartridges are more compact, they can store from about 15 to 50 times more data than diskettes, and they have a lower cost per megabyte.
Tape cartridges, such as the Scotch DC 300XL data cartridge made by 3M Co., are commonly used for data storage in cartridge drives. Briefly, this type of standard tape cartridge includes a 1/4-inch magnetic tape enclosed within a case. The tape is driven, in part, by an internal capstan, a portion of which is exposed at an edge of the cartridge case. When the cartridge is inserted into a receptacle in the tape drive unit, the exposed portion of the capstan engages a drive capstan driven by the tape drive motor for driving the tape. The tape cartridge also includes a door near a corner of the case. The cartridge door is normally spring-biased to a closed position for protecting the tape during storage and transport. When the cartridge is inserted into the tape drive unit, the door is tripped open to expose a portion of the tape for engaging the magnetic read/write head of the tape drive unit. The head projects into the cartridge envelope to contact the tape under the proper operating tension. The mechanism for guiding the cartridge into the receptacle not only trips open the door; it also prevents the door from contacting the read/write head when the cartridge is being inserted or removed.
The magnetic tape cartridges used in magnetic tape drives are manufactured according to industry standards approved by the American National Standards Institute (ANSI). Magnetic tape drives, including the larger 1/2-inch tape drives, have been able to replace the industry standard larger disk drives, such as the 8-inch, 101/2-inch and 14-inch disk drives. However, the standard 1/4-inch tape drive units have not been able to replace either the 51/2 inch minifloppy disk drive or the Winchester-type disk drive, because the ANSI standard size 1/4-inch tape cartridge has been too large to fit into a tape drive unit that meets the industry-standard exterior dimensions of the 51/4 inch disk drives. For instance, the standard exterior width of a 51/4 inch disk drive package is 5.75 inches. With the ANSI standard size tape cartridge inserted in a standard tape drive and with the cartridge door held open to expose the tape, the cartridge case and the cartridge door in its open position cover a distance of 5.765 inches, i.e., a distance greater than the standard 5.75-inch width of the smaller disk drives.
The present invention provides a door opening mechanism for a magnetic tape drive that allows an ANSI standard tape cartridge to be inserted into a tape drive package having the same industry standard exterior dimensions as the 51/4 inch disk drives.
The ANSI standard exterior dimensions of a 1/4-inch tape cartridge are 4 inches by 6 inches (when the cartridge door is closed). U.S. Pat. No. 4,498,112 entitled "Tape Cartridge Receptacle", discloses a tape drive unit which allows a 1/4-inch tape cartridge to be inserted into a tape drive housing having the same exterior dimensions as the 51/4 inch disk drives. In that tape drive unit, the cartridge is front-loaded into the receptacle, i.e., the cartridge is inserted with its long dimension facing the mounting slot of the front wall of the tape drive housing. As the cartridge is inserted, the door opening tab on the cartridge door engages a cam on the cartridge guide rail which opens the door and holds it partially open, but open sufficiently to allow normal contact between the head and the tape. The amount of space taken up by this tape drive unit adjacent a computer console can be reduced if the tape drive housing is rotated 90.degree. so that its short dimension (the end face of the unit) faces forward adjacent the computer console. However, this would require loading the cartridge into the tape drive unit endwise, i.e., inserting the cartridge lengthwise with its short dimension facing a shorter mounting slot in the end wall of the housing. If the tape cartridge is loaded endwise, the door opening tab cannot be engaged in the previously described manner because the tab and the door axis of rotation lie in the same plane as the direction of insertion. Moreover, the read/write head would normally interfere with sliding the cartridge case endwise into the tape drive unit. The head would block the cartridge because the head normally protrudes into the tape cartridge envelope.
The present invention provides a tape drive unit having a cartridge door opening mechanism which cooperates with a movable read/write head to allow a tape cartridge to be inserted endwise into the housing without interference with the read/write head. The read/write head is held in a retracted position, and the cartridge door is opened near the end of the cartridge travel into the unit. The door opening mechanism contacts the tab on the cartridge door and holds the door open at a position less than its fully open position. This allows the cartridge to fit within the confines of the desired 51/4 inch exterior dimension of the housing. Once the tape cartridge is in place in the unit, the read/write head is moved into an operating position for applying the proper operating tension to the tape. The head is retracted prior to removing the cartridge from the tape drive housing.
There is a need to ensure that the door opening mechanism which contacts the cartridge door opening tab does not cause undue wear on the cartridge door opening tab. If the tab becomes excessively worn during use, the cartridge can jam in place in the unit with the door not open sufficiently, in which case the read/write head can collide with the door. It is also desirable to open the cartridge door to as wide an angle as possible, within the confines of the 51/4 inch limitation. This would allow use of a larger read/write head.
The door opening mechanism of this invention produces essentially no wear on the cartridge door opening tab during use. It also can open the door to the maximum allowable extent. In addition, there are other advantages over ramps, cams, or toggling mechanisms that may be used to open a cartridge door.